Borated-silicate-starch laminating adhesives and manufacture of combined fiberboard therewith



Dec. 4, 1956 R. H. sAMs 2,772,996

BoRATED-SILICATE-STARCH LAMINATING ADHEsxvEs AND MANUFACTURE OF COMBINEDFIBERBOARD THEREKITH Filed OC. 15, 1953 United States Patent OBORATED-SILICATE-STARCH LAMINATING AD- HESIVES AND MANUFACTURE OFCOMBINED FIBERBGARD THEREWITH Robert H. Sams, Darby, Pa., assignor toPhiladelphia Quartz Company, Philadelphia, Pa., a corporation ofPennsylvania Application October 15, 1953, Serial No. 386,230

17 Claims. (Cl. 154-138) This invention relates toborated-silicate-starch laminating adhesives and manufacture of combinedfiber board therewith; and it comprises a novel adhesive containing fromabout 1.5 to 10 percent by weight of a raw unswollen starch-likematerial, having the property of swelling by hydration before going intosolution when heated in water to temperatures within the range of fromabout 55 to 80 C., usually from about l to 25 percent QLaLnely-dividedsiliceonsmaterial, such as clay, and from abo`ut`02 tS'percent by weightof an alkali metal hp ratefg from about 15 to 150 percent borate basedon the starch'c'oritent of the adhesive, all dispersed in anaqueouis'dsofuiio'n of sodium" silicate constituting at leastRout'Opercent of the adhesive as a whole; the said silicate solutionhaving a viscosity within the range of from about 0.25 to l5 poises anda gravity of from about 30 to 50 B. at 20 C., and a percent ratio ofNazO to SiOz within the range of from about 1:2 to l:4.2; said adhesivehaving an overall viscosity at operating temperatures of from about 0.2to 15 poises and a filter test at operating temperatures of from about 2to 20 cc. and, in the case of a composition free from clay, up to about30 cc.; said adhesive having a Viscograph curve with a knee at aviscosity of from about 0.2 to 3 poises which lies between about 70 and85 C. and, in the case of a composition free from clay, between 60 and75 C.; said adhesive having the characteristic property of increasing inviscosity at a rate substantially higher than that of a similar adhesivefree from said alkali metal borate when heated to temperatures withinthe range of from about 55 to 90 C. My invention also includes a processof using the described adhesive in the making of combined ber board onone of the conventional high-speed laminating machines wherein theadhesive is a plied to the face of one ply and at least oneonaIA-plyiseoml Friedeniett'vith, the 'applied adhesive being' giatly'T1-cated tdtemperajures causiri'gwswlliiig'ofits starch-like Eaenawhereby a flash bond is prducedf'all asinore fully hereinaffrsetforth and 'asclaimedfY In the copending application of Robert L.Kreyling, Serial No. 169,537, led June 21, 1950, now Patent No.2,669,282, a starch-clay-silicate adhesive is described which has foundlarge scale commercial use in the production of corrugated paper board.This adhesive has been generally recognized as providing the fastest setand forming the best bonds of any of the silicate adhesives previouslyused in the laminating art. Plants producing box board, however, arecontinuously looking for adhesives having faster sets and producingbetter bonds so that they can run their combining machines faster andproduce more box board per minute.

While making an extensive series of tests in the attempt to tnd ways ofimproving the Kreyling adhesive I made the surprising discovery that theaddition of a small amount ofhoraLtgja typical starch-clay-silicateadhesive p f. the l reyling type is ca "fncreas-irgvtbe viscosity,v.time Citicalfcombining tempera ure range, y a.

weight of the starch in the adhesive.

ICC

factor which is usually several hundred percent. This discovery, madewith a standard Viscograph, a product of the Brabender Corp., in whichthe adhesive is heated gradually up to a maximum temperature of about C.followed by cooling, while a record of the viscosity is being made,would indicate that a much quicker set or grab" would be produced by theborated composition on a combining machine. Subsequent extensive testsmade on commercial combining machines have fully conrmed the conclusionsreached as a result of these Viscograph tests.

l t may seem strange that this viscosity-increasing eiect of borax onstarch-silicate adhesives had not been discovered and reportedpreviously, especially since borax has been added to both starchadhesives and to silicate adhesives individually, at least in smallproportions. lt appears that l am the rst to have added borax to anadhesive containing both starch and silicate in such proprotions as toproduce a substantial viscosity increase upon heating of the adhesive.

My tests have shown that the described viscosity-increasing effectoccurs over a borate concentration in the starch-silicate adhesivesranging from about 0.2 to 5 percent by weight, based on the weight ofthe adhesive, or from about 15 to 150 percent by weight, based on theThe effect of even 0.2 percent of borax is clearly evident in Viscographtests but in practical combining operations the effect produced by thisaddition seems to be so small that it cannot readily be detected. Whenthe borate content is increased to 0.5 percent, however, the effectproduced is clearly apparent even in commercial operations; hence it ispreferred to include at least about 0.5 percent of a borate in the newadhesive. The upper limit of percent based on the weight of the starchcontent is caused because the borax seems to make the starch lumpy whenits content reaches this upper limit. It is possible that, if some wayof eliminating this lump formation could be discovered, even higherconcentrations of borax could be employed. But since the use of suchconcentrations would not be as economical, this is more of academic thanpractical interest.

I have found that the viscosity-increasingeifectV is pg; duced byallofthe norma'aikllgtlborates, for example sodiurngid,potassiumY meta andtetra boraes. lrlc'scause diiiculties from frothing as the adhesive isheated and apparently react with the starch content; hence the use ofperborates is not recommended. There is little difference between theeffects produced with sodium metaborate and sodium tetraborate. Boricacid is an equivalent and, since it forms a sodium borate as soon as itcomes in contact with the sodium silicate present in the adhesive, theaddition of boric acid to the adhesive can be considered as beingincluded within the scope of the term alkali metal borate as used in thefollowing description and in the claims.

In the case of starch-clay-silicate adhesives the presence of clay or anequivalent has been found to be necessary. This material increases thefilter tests and has the functions of imparting thixotropic propertiesto the adhesives and preventing undue penetration of the adhesives intothe boards to be laminated before setting of the adhesives.gmmglayontent of about 4 percent in starch-clay-silicate adhesives isCQBSdt-:redisselll- I llimiwtmade the supnsing discovery that, if asmall amount of borax is included in the adhesive compositions the rateof setting is actually increased to such an extent that the presence ofclay to prevent penetration becomes of much less importance and withsome formulations it is possible to dispense with the clay entirely. Theexplanation apparently resides in the fact that in the conventionallaminating machines the adhesive is heated to setting temperatures sorapidly and the borated adhesives set so rapidly that these adhesivesset before they have time to penetrate unduly. I usually prefer toinclude clay in the new adhesives, however, since it is the leastexpensive component and since it contributes to the value of theadhesives, increasing their adaptibility and their operating life.

In the case of clay-silicate adhesives and starch-claysilicate adhesivesthe so-called filter test can be used to determine whether an adhesivewill penetrate unduly and whether it has satisfactory thixotropiccharacteristics. This filter test is described in Patent No. 2,239,358.For these prior adhesives a filter test of from about 3 to 15 cc. isessential for high speed laminating operations. But owing to theviscosity increasing effect of the borate addition, described above, thefilter test in the case of the present adhesives has lost most of itssignificance. In the case of my borated adhesives containing say from 1to 2% of clay, the filter test may be as high as 20 cc. and in the caseof clay-free adhesives the filter test may range up to 30 cc.Fortunately I have been able to devise another convenient test for theoperativeness of my borated adhesives which is even more significantthan the filter test for the clay-silicate and starch-clay-silicateadhesives. This is the standard Viscograph test.

The Viscograph test is described in U. S. Patent No. 2,554,035 andconsists in recording the viscosity changes of the test adhesive whileit is being heated without evaporation f moisture at a rate of about 1.5C. per minute up to a temperature of 95 C. followed by cooling at aslightly more rapid rate. The viscosity is then plotted against thetemperature, as shown in the accompanying drawing. In this showing,

Fig. 1 shows a series of Viscograph curves in which the viscosities areplotted as ordinates against the temperatures as abscissas.demonstrating the effect of borax on the shapes and positions of thecurves, while Fig. 2 shows a similar set of curves designed primarily toshow the effect of varying starch content on the shapes and positions ofthe curves.

In making the Viscograph curves shown in the two figures of the drawing,the following compositions were employed, the numerals and lettersdesignating the compositions corresponding to the numbers and letters onthe curves of the drawing.

Curve ].-5.5 parts of starch dispersed in 7.0 parts of water, to which79.0 parts of N silicate were then added (no clay; no borax).

Curve 2.-5.5 parts of starch dispersed in 7.0 parts of water, to whichwas added 79 parts of N" silicate, followed by 8.5 parts of Barden clay(no borax).

Curve 3.-0.2 part of borax dissolved in 6.8 parts of water, 5.5 partsstarch dispersed in the solution, 79 parts of N silicate mixed in andthen 8.5 parts of Barden clay.

Curve 4. 0.5 part of borax dissolved or disposed in 6.5 parts water, 5.5parts starch dispersed in the solution, 79 parts of N silicate mixed inand then 8.5 parts Barden clay.

Curve 5.1 part of borax dispersed in 6 parts water, 5.5 parts starchdispersed in the mixture, 79 parts of N silicate mixed in and then 8.5parts Barden clay.

Curve 6.-2 parts of borax dispersed in 5 parts water, 5.5 parts starchdispersed in the mixture, 79 parts N silicate mixed in and then 8.5parts Barden clay.

Curve 7.-3 parts of borax dispersed in 4 parts water, 5.5 parts starchdispersed in the mixture, 79 parts N" silicate mixed in and then 8.5parts Barden clay.

Curve 8.-5.5 parts of starch dispersed in 6 parts water, 1 part boraxadded and then 79 parts of N silicate mixed in (no clay).

Curve A (Fig. 2).-1 part borax dissolved or dispersed Y 4- 2.5 partsstarch dispersed in the mixture, 80.5 parts of N silicate mixed in andthen 8.5 parts Barden clay.

Curve C. 1 part of borax dispersed in 7 parts of water, 3.5 parts starchdispersed in the mixture, parts N" silicate mixed in and then 8.5 partsBarden clay.

Curve D.-1 part of borax dispersed in 6.5 parts of water, 4.5 partsstarch dispersed in the mixture, 79.5 parts N silicate mixed in and then8.5 parts Barden clay.

Curve E.-1 part borax dispersed in 6 parts of water, 5.5 parts starchdispersed in the mixture, 79 parts N silicate mixed in and then 8.5parts Barden clay.

Curve F.-2 parts borax dispersed in 5 parts water, 5.5 parts starchdispersed in the mixture, 79 parts "N silicate mixed in and then 8.5parts Barden clay.

Curve G.-2 parts borax dispersed in 7 parts water, 2 parts starchdispersed in the mixture, 80.5 parts "N" silicate mixed in and then 8.5parts Barden clay.

The N silicate used in these tests had a gravity of 41.0 B. and a weightratio of SiOz to NazO of 3.23. It contained 8.90% NaaO and had aviscosity of 1.8 poises at 20 C. The Barden clay was a high gradekaolinite clay from 1. M. Huber Corp. The starch was #7021 pearl cornstarch from Anheuser-Busch, Inc.

It will be noted from the curves of liig. l that the addition of boraxto a starch-clay-silicate adhesive has the effect of moving theviscosity minimum of the Viscograpli curves in the direction of lowertemperatures and higher minimum viscosities. Thus while a standardstarch-claysilicate adhesive (curve 2) produces a Viscograph curvehaving a knee at about 87 C. and a viscosity of 0.7 poise. the knee ofcurve 7 for a similar adhesive containing 3% borax lies at about 68 C.and 2.7 poises. The most striking` effects produced by the boraxaddition, however. are the greatly accelerated increase in viscosity perdegree rise in temperature following the knees of the curves and theincrease in the maximum viscosity reached during the test. In curve 2,fot' example the viscosity rises gradually starting at about 87 and themaximum viscosity reached is only about 2 poises during the heatingcycle. In contrast, curve 7, for a composition containing 3% borax,shows an almost vertical rise in viscosity to a value which evidentlylies far off the chart. Curve 3, as compared with curve 2 shows that theaddition of only 0.2% borax produces a pronounced increase in themaximum reached during the heating cycle and in the rapidity of the risetowards this maximum. A comparison between curves 1 and 2 shows theeffect of the addition of 8.59? clay upon a starch-silicate adhesive,while a comparison between curves 8 and 5 shows the elect of theaddition of 8.5% clay upon an adhesive of similar composition butcontaining 1% borax.

The curves in Fig. l aiso show that the effect of borax additions tostarch-silicate adhesives, in changing the positions of the knees of theViscograph curves and increasing the rate of increase in viscosity, isconsiderably reduced 0r masked when clay is present in the compositions.Thus, while the addition of 1% borax to the clayfree composition ofcurve 1 causes the knee of the curve to drop from about 92 to 65 (seecurve 8), in the case of similar compositions containing 8.5% clay(curves 2 and 5) the corresponding drop is from about 88 to 80Dl causedby the addition of 1% borax. Considered from this single standpoint thepresence of clay in the compositions may be disadvantageous. Theadvantages gained by the presence of clay in my adhesives, however,usually outweigh this one disadvantage.

As a result 0f making the curves shown in Figs. 1 and 2 of the drawingand a large number of additional curves. as well as making manypractical corrugating tests on the present adhesives, I have been ableto correlate the compositions and the properties which are essential inboraxstarch-silicate adhesives to make them suitable for highspeedcorrugating operations. Thus these adhesives should contain from about1.5 to 10% of a raw unswollen starchlike material having the property ofswelling by hydration before going into solution when heated in water totemperaturcs within the range of from about 55 to 80 C., from about 0.2to 5% of an alkali metal borate or from about 15 to 150% based on thestarch content of the adhesive, all dispersed in an aqueous solution ofsodium silicate constituting at least about 50% of the adhesive as awhole; said silicate solution having a viscosity within the range offrom about 0.25 to 15 poises and a gravity of from about 30 to 50 B. at20 C., and a percent by weight ratio of NazO to SiOz within the range offrom about 1:2 to 1:4.2; said adhesive also advantageously containingdispersed therein from about 1 to 25% of a finely-divided siliceousmaterial having an average particle size not substantially exceedingabout 2 microns, such as clay, having an overall viscosity at operatingtemperaturcs within the range of from about 0.2 to 15 poises, a filtertest at operating temperatures of from about 2 to 20 cc. and, in thecase of clay-free compositions, up to 30 cc. or over; said adhesivesproducing Viscograph curves with knees at viscosities of from about 0.2to 3 poises which lie between about 70 and 85 C. and, in the case ofclay-free compositions, between 60 and 75 C. The described compositionsall have the characteristic property of increasing in viscosity at arate substantially higher than that of similar adhesives free from saidalkali metal borate when heated to temperatures within the range of fromabout 55 to 90 C.

l usually preiermto use a clay as the finely-divided solid `s i lice9psY componentmrf Yry adhesives but any'bthe'r s ilicous materials canbe used provided that they are 'gfglloiddaln hp enessm This means thatfrom about 92 to 99% of the material should pass a 325 mesh screen. Atleast 50% should have a particle size of 2 microns or less. Diatomaceousearth, fullers earth, ball clay, china clay and calcined kaolinites arearti ular'ly suitable. Equally suitable are the reactive sillceoussynthetiep'roducts for example the amorphous precipitated silicas, suchas Santocel and Hysil and acid treated kaolinites, such as Zeolex 20. Itrequires at least about 1% of siliceous material to produce anappreciable effect on the properties of the adhesive, The effectprodugedcpends upon the particle size weintherls material. For ex-Vampieitri'equirswriiroximately 12% of china or ball clay to produce theeffect produced by only 1.5% of Wyoming bentonite or by 6% of a SouthCarolina kaolin or by 5% of diatomaceous earth. No more should be usedthan is required to produce a viscosity of from about 0.5 to 5 poises atoperating temperatures for the manufacture of corrugated paper board orfrom about 5 to 15 poises at operating temperatures for the manufactureof solid ber board. The use of borax, as in the present adhesives,permits a substantial reduction in the quantity of clay required in theadhesives or the complete elimination of this component.

4More important, the use of borax in my adhesive enables a substantialreduction in the starch content of the adhesive, as compared withadhesives free from borax. Thus a -licate adhesive containing 3% starchand 1% ax amm-clayhas a-Viscograph curvewhich rises in viscosityduringitheih-eting cycle to a maximum of about 2 poises, as also does asimilar adhesive containing 5.5% starch and 8.5% clay. One percent boraxis thus equivalem to abOuLZB/Lastirbsqcinsmesmmaxifm''mwvicity. But theborax-containing adhesive is 'htrfr-h-igh speed laminating for thereason that the knee of its Viscograph curves lies at least 7 lower.This shows that setting of the borated adhesive takes place at a lowertemperature and hence more rapidly when passed through a laminatingmachine. Since starch is the most expensive component of theseadhesives, a substantial saving is effected in the use of borax with aconsequent reduction in the starch content.

Morevimportant, the borated adhesives produce a better bond, one that ismore uniform and one that is substantially free from non-bonded spots.Apparently the latter eiect is due to the fact that the borax increasesthe swelling of the starch during the bonding operation and this tendsto bridge any gaps between the plies as the latter are being united.There is also a greatly reduced tendency for the finished board to warpwhen borated adhesives are employed, this being due probably to the moreuniform bond produced. There is less dusting of the adhesive duringprinting of the tinished board. And viscosity control of the adhesiveduring the combining operation is less critical. This makes the adhesivemore versatile. It is also true that less adhesive per running foot ofboard is required to produce bonding, this being due, presumably, togreater swelling of the adhesive during the laminating operation.

As in the case of the Kreyling adhesive, my new adhesive has a life atordinary temperatures which is substantially indefinite. The borax actsto some extent as an antiseptic and this, togethewhjjxg'ftm'f'myadhesives, efechvel'y-emmny tendency for the stc'lihtio decompose. It isimportant that the adhsives contain no moremabout 2 percent protein andhence the starch material emyedsh'ouldcohtain no more than from about; 5to 7% of protein.

All types of starch can be -usedn my adhesives. Pota'tsiarhndamicst'chsvg'ive Viscograph curves f'siglitly diierentushapev than those producedwith pearl corn starch but the adhesives are equally effective. Othersuitable starches are rice starch, sago, tapioca and cassava starches,arrowroot, arum, the so-called moss starch, inulin and glycogen. Allother starch-like materials, having the property of swelling beforegoing into solutimylggjeated with waet'einperati's'"within the range offromm'about 55 to 80 C. are operative. Thesesubstancs"'n'clude' s tarchderivatives, such as methyl cellulose, starch ester's-dunpaiconate, thesodium salt of palconic acid, an alkali-soluble material extracted fromredwood bark with sodium hydroxide which has been shown to consistmainly of a partially methylated phenolic acid, containing aliphatichydroxyls, phenolic hydroxyls, and carboxyl groups in the ratio of2:413; see an article by Frank A. Kottwitz and L. D. Forman in Ind. Eng.Chem., 40, 243 (1949); supplied by The Pacific Lumber Company anddescribed in their Technical Bulletin No. T-4 (1950); "Silvacon, acomplex mixture of the salts of lignin and tannic acids derived fromspruce wood, supplied by Weyerhaeuser Timber Company, more fullydescribed in Western Pulp & Paper, vol. 1, #4, pages 12-14 (1948);SolkaL a cellulose pulp preparation made from wood bers, described inThe Handbook of Material Trade Names, Zimmerman and Lavine, 1946,published by Industrial Research Service, Dover, N. H., supplied by theBrown Company, and Solkaoc which is fully described on pages 131 and 132of the Chemical Materials Catalog (1949-1950), supplied by the BrownCompany. The term starch-like material as used in the following claimsis intended to include these materials.

The s`ilicjate solputionmused as the liquid or aqueous phase ofmy`adh'esive may, as indicated previously, have a percent ratio of Na2Oto SiOz within therrangeof from about 1 to 2Y to 1 to 42 anda 'viscosityof fromabout Olo-lS-o-is-es-TTC. The permissible range of gravities ofthe silicate solution ranges from about 30 to 50 B. at 20 C., the highergravities being employed with the more alkaline silicates. For adhesiveswhich are to be applied hot, i. e. which are heated before application,the liquid phase gravity should lie between about 32 and 50 B., whilefor adhesives which are to be applied at room temperatures the range isfrom about 30 to 48 B. Commercial silicate solutions can be employed,usually with the addition of small amounts of water, or solid silicatescan be dissolved in the proper quantities of water required to producethe required gravities. Owing to the fact that the more alkaline sili-Cates of a given concentration have the lower viscosities it is possibleto employ more clay and/or more starch with the former.

My invention can be explained in greater detail by reference to thefollowing specific examples which represent practical operatingembodiments thereof.

The adhesive compositions designated previously as 3 to 8 and B to G,corresponding to the similarly designated curves in the drawing,constitute specific operating embodiments of this invention. Thefollowing compositions represent additional specic examples of myadhesives:

Example 1 A series of adhesives was prepared and Viscograph tests wererun on each. These adhesives had the fcllowing compositions:

#1. 79% N silicate, 6% water, 5.5% potato starch, 8.5% clay and 1%borax.

#2. 79% N silicate, 6% water, 5.5% potato starch, 8.5% clay, 0.5% boraxand 0.5% isopropanol.

#3. 79% N" silicate, 6.0% water, 5.5% corn starch, 8.5% clay. 0.5% boraxand 0.5% isopropanol.

#4. 79% "N" silicate, 6% water, 5.5% corn starch, 8.5% clay and 1.1%sodium metaborate8H2O- #5. 79% N silicate, 6% water, 3.7% starch, 8.5%clay, 1% borax and 1.8 soy flour.

#6. 79 parts N" silicate, 6.0 parts water, 5.5 parts starch, and 1 partborax (no clay).

The above adhesives were run in the standard Viscograph test. Theviscosities recorded during the test are indicated in the followingtable for the temperatures indicated.

Initial Visi Minimum vViscosity, Viscosity, Adhesive cosity, 30Viscosity, 10 minutos Maximum C., poiscs Poises at after min. at C.

c at C. l 1, 9 i 1, 0. 63 3. 8. 83 5. 2, 95 2.2 i 1.262 28.82 4.s,95 2.ol 1.1,73 4.2,83 6.6,95 1.8 0.8,? 1.9, 86 5. 3, 95 2.6 l 1.s.73 1.7,s23.7,95 1. 25 1 0. 6, 73 1. 2, 83 thick, 93

Example 2 10 parts by weight of Anheuser-Busch #7021 pearl com starchwere wet with 10 parts of water, 74 parts of "N silicate were added withstirring. then a slurry of 3 parts of borax in 3 parts of water wereadded with more stirring. The resulting adhesive contained 10% starch,13% water, 3% borax and 74% of N silicate Example 3 parts of .$7021starch were wet with 5 parts of water, 50 parts of "S-35 silicate wereadded with stirring, followed by a slurry of 1 part borax in l part ofwater, and then 20 parts of Barden clay and 1S parts of water addedalternately in halt-portions with further agitation. The S-35 silicatehad a ratio of 1Na2O:3.75 SiOz and a gravity of 35 B. The resultingadhesive had a com- 8 position of 5% starch, 24% water, 1% borax, 50%S-35 and 20% clay. The following data were obtained in a Viscographtest:

C.: Poises 30 0.92 44 0.94 58 1.00 1.16 1.51 72 2.25 '/3 4.00 74 7.16 7510.33 76 13.19 77 Thick Example 4 5.5 parts #7021 starch were wet with 6parts water. A syrup containing 0.5 borax dispersed in 0.5 partdiethylene glycol was added with stirring. One hour later 79 parts of N"silicate were added with stirring and finally 8.5 parts Barden clay weremixed in. The resulting adhesive contained 5.5% starch, 6% water, 0.5%borax, 0.5% diethylene glycol, 79% N silicate and 8.5% clay. AViscograph test provided the following data:

C.: Poises 30 2.11 44 1.47 58 1.19 73 1.01 78 0.98 81 1.01 83 1.24 851.59 88 2.41 91 4.00 95 5.15

Example 5 5.5 parts of #7021 corn starch were mixed with 5 parts water,a sludge containing 1 part of boric acid crystals in 1 part water wasadded with stirring. 79 parts of N" silicate were mixed in and the batchwas worked several hours until a lump-free blend was obtained. 8.5 partsof Barden clay were then stirred in. The resulting adhesive contained5.5% starch, 6.0% water, 1% boric acid, 79% of N silicate and 8.5% clay.A Viscograph test gave the following data:

Example 6 In this example the flow characteristics of two adhesives werecompared, one being a borated clay-starchsilicate adhesive containing80% N silicate, 7% water, 3.5% starch, 1% borax and 8.5% clay, while theother was a clay-starch-silicate adhesive containing 79% N silicate, 7%water, 5.5% starch and 8.5% clay. In this test the spindle of aBrookfield Viscometer was operated so the rotational resistance itencountered from the liquid could be measured at 4 different speeds. Thestress measurements were translated to apparent viscosities and thesewere plotted against calculated rates-of-ow. ln both cases curves wereobtained whose apparent viscosity decreased with increasing rate-of-ow.The borated adhesive had a slightly lower apparent viscosity throughoutthe range of rates-of-iiow, which means that it could be pumped moreeasily at operating temperatures. The borated adhesive was alsoappreciably cheaper owing to its lower starch content. Viscograph testsshowed that the borated adhesive started to set at a lower temperatureand it increased in viscosity more rapidly at bonding temperatures. Inother words, the borated adhesive is superior in all characteristicsrequired of a high-speed laminating adhesive.

Example 7 A plant test was run with a borated adhesive made by mixing292 pounds of water, 40 pounds of borax, 150 pounds of pearl cornstarch, 350 pounds of Suprex clay (J. M. Huber Corp.) and 3268 pounds ofN silicate. This gave an adhesive containing 7.1% water, 1% borax, 3.7%starch, 8.5% clay and 79.7% N silicate. This adhesive was run for 2weeks on a commercial corrugating machine, the adhesive being heated toISO-'PFT'I was found that the average hourly production rate could bemaintained at 72,000 to 80,000 square feet per hour, whereas with astandard clay-starch-silicate adhesive production had not exceeded 68,00to 70,000 square feet per hour.

Example 8 Another plant test was run with an adhesive prepared by adding40 pounds of borax to a mixture of 300 pounds of water, 200 pounds ofstarch, 300 pounds of clay and 3170 pounds of 40 B. N silicate. Thisproduced a mixture containing about 1% of borax or 20% based on thestarch content. The plant had been running successfully using astarch-clay-silicate adhesive but, when the new adhesive was substitutedfor this, immediate improvement in the bond on both the single face anddouble backer sides was noted. At 225 feet per minute and with 31 feetof hot plates in the double hacker section, the bond set so rapidlyright out ot the edge of the board that the glue pattern could not betested at the end of the machine.

Example 9 In this plant test an adhesive containing 1% borax, 7.5%water, 7.5% Barden clay, 3.7% starch and 80.3% N silicate was directlycompared with a borax-free adhesive containing 5.3% starch, 7.5 clay and80.3% N silicate. When the new adhesive was used on the double backerside only it was found to be tackier but to set slightly slower than theadhesive containing 5.3% starch. But an execellent bond was obtained ondouble wall board at 280 feet per minute and with 47 pound liners at 300feet per minute. In a two Weeks run it was determined that this adhesivewas at least as good as that containing the higher starch content. Itgave less trouble from loose edges with wet liner, and less dusting wasobserved. The boxes made with this adhesive had the highest compressionstrength ever obtained in that mill. From top to bottom the compressionwas 120% and from end to end 114%.

A sample of this adhesive was tested on the Viscograph in thelaboratory. It had an initial viscosity of 1.4 poises at 30 C. Theminimum viscosity was reached at about 76 C. and 0.9 poise, while themaximum viscosity at 95 C. was 3 poises. After cooling the viscosity was3.7 poises.

The C-ute board made with this adhesive weighed about 134 pounds per 100square feet and had a caliper between 0.159 and 0.163. The at crushresistance averaged 29 pounds per square inch and adhesive bondstrengths averaged 46 pounds per foot length of ute tip 10 on the singlefacer side and 53 pounds per foot on the double backer side. The eectivetear coverage for both was 100%. For visual rating the single face sidewas rated good while the double backer side was rated perfecta veryunusual achievement.

Example 10 Another test was run in a plant of a company which had beenbonding its corrugated board at 420 F. P. M. using a standard adhesivecontaining 5.5% starch, 8.5 clay, 79% of "N silicate and 7% water.Comparative tests were run with two borated adhesives the first of whichcontained 1.1% borax, 5.3% starch, 8.5% clay, 78.1% N silicate and 7%water, and the second 1.1% borax, only 3.2% starch, 8.5% clay, 80.2% Nsilicate and 7% water. Both of these borated compositions producedcompositions produced an obvious improvement of the bond and the testswere considered highly successful by the operators.

Example 11 In another plant, which had been using an adhesive containing5.3% starch, 7.3% water, 8.5% clay and 79% N" silicate, a test was madewith a borated adhesive containing 1% borax, 5% corn starch, 7.3 water,7.5% clay and 79.2% N silicate. The plant personnel immediately notedthat a better bond was being produced.

Example 12 In another plant test the standard starch-clay-silicateadhesive described above was replaced with an adhesive containing 79% Nsilicate, 8.5% clay, 3.7% pearl corn starch, 1% borax, 1.8% soy our, and6.0% water. Although the new adhesive had some tendency to foam, bettertack and faster set were obtained and the cost of the adhesive wasreduced substantially as compared with that of a straight silicateadhesive.

Example 13 In still another plant test a mixture was made containing 300pounds water, 50 pounds borax, 200 pounds pearl corn starch, 300 poundsof clay and 290 gallons of silicate. The composigtiqnjqf this adhesivecorresponded to 7.1% waterfllf; borax, 4.8% starch', 7.1% clay and 79.8% si licate. It weg used at 136 F. with one section of six hot'platesat 20 pounds steam pressure (gauge) and a second section of 33 plates at110 pounds. At a speed of 425 to 450 F. P. M. in one eight hour shift141,000 feet of board were produced. A better bond was obtained withimproved at crush resistance and no warp. A better printing surface wasobtained. This test was run for 10 days and a better bond wasnoticeable, particularly with wet liners.

All of theflgoratedadhesiveswhich have been described in the foregoingare well adapted for use in the highspeed manufacture ofcombinedjiberboard. ln this process lthe adhesive is applied to Cmd atleast one additional ply is combined therewith, the applied adhesivebeing immediately heated to temperatures causing the swelling of thestarch-like material contained therein, whereby a ash bond is produced.While my adhesives can be used at ordinary room temperatures inlaminating operations it is somewhat more advantageous to preheat themwithin the range of from about 40 to 80 C. before they are applied. Itis also advantageous to have the plies preheated to temperatures withinthe range of from about 80 to 105 C. if the highest speeds are desired.When applied in this fashion the aqueous phase of the adhesive shouldhave a viscosity of from about 1 to 8 poises and a gravity of from about32 to 50 B. at 20 C. On the other hand if the adhesive is applied atroom temperatures its aqueous phase should have a viscosity of fromabout 0.25 to 1.5 poises at 20 C. and a gravity of from about 30 to 48B. at 20 C. In the production of solid ber board the over-all viscosityof the adhesive at operating temperature is preferably from about to 15poises while in the production of corrugated paper the over-allviscosity should be from about 0.5 to 5 poises at operatingtemperatures. When thus used my adhesives are capable of combining boardat speeds which are substantially higher than those achieved with anyother adhesives with which I am familiar and which are within the sameprice range.

While I have described what I consider to be the best embodiments of thepresent invention it is evident of course that various modifications canbe made in the specific procedures and proportions of components thathave been mentioned without departing from the purview of thisinvention. Thus, while I have described adhesives containing smallamounts of isopropanol and soy our, there are several other materialswhich can be added to make the adhesives best fitted for particularindustrial applications. Thus, hurnectants such as glycerine or analginate which may serve as plasticizing and toughening agents,emulsifiers such as carboxymethylcellulose, and small amounts ofreactive materials such as aluminum chloride which add water-resistance,can be added with advantage for special uses. My adhesives areparticularly adapted to high-speed laminating operations in themanufacture of tiber board and the various specific proportions whichhave been set out previously are critical for adhesives suited to thisparticular use.

While I have set out rather broad operative ranges of components in theforegoing best results in high-speed laminating operations are obtainedwith somewhat narrower ranges. These are from about 2 to 5% of starch,from about 4 to 10% of clay, from about 0.5 to 4% alkali metal borate orfrom about 20 to 100% borate, based on the weight of the starch. andfrom about 75 to 80% silicate solution in which the per cent weightratio of NazO to SiOz is within the range of from about 1:2.5 to 1:4;the silicate solution (aqueous phase) having a viscosity within therange of from about 0.25 to 15 poises and a gravity of from about 30 to50 B. at 20 C. These preferred adhesives have an over-all viscosity atoperating temperatures of from about 0.5 to 15 poises and a filter testat operating temperatures of from about 3 to 15 cc.

My new adhesives can be used in many other applications whereinquick-setting strong bonds are required to be produced at a minimumcost. In these cases various modifications can be made in the specificproportions which have been listed. Other modifications of thisinvention which fall within the scope of the following claims will beimmediately evident to those skilled in this art.

What l claim is:

An adhesive composition particularly adapted for use in the high-speedmanufacture of combined ber board, which comprises from about 1.5 to percent by weight of a raw unswollen starch-like material which has theproperty of swelling by hydration before going into solution when heatedin water to temperatures within the range of from about 55 to 80 C.,from about 15 to 150 percent by weight of an alkali metal borate basedon the starch like material in the adhesive, and usually from about l to25 percent by Weight of a finely-divided solid siliceous material havingan average particle size not subst-atilly'exc'edig 2 microns, alldispersed in an aquegus solutiorrof` sodium silicate which constitutesat least about 50 percent by weight of the adhesive as a whole; the saidsilicate solution having a viscosity within the range of from about 0.25to poises and a gravity of from about 30 to 50 B. at 20 C. and a percentratio of NazO to SiOz within the range of from about 1:2 to 1:42; saidadhesive having an over-all viscosity at operating temperatures of fromabout 0.2 to l5 poises, a iilter test at operating temperatures of fromabout 2 to 20 cc. and, in the case of compositions free from clay, up toabout 30 cc. and having a Viscograph curve with a knee at a viscosity offrom about 0.2 to 3 poises which lies between about 70 and 85 and, inthe case of compositions free from clay, between about 60 and 75 C.;said adhesive having the characteristic property of increasing inviscosity at a rate substantially higher than that of a similar adhesivefree from said alkali metal borate when heated to temperatures withinthe range of from about 55 to 90 C.

2. The adhesive of claim 1 wherein said starch-like material is rawcornstarch.

3. The adhesive of claim 1 wherein said starch-like material is rawpotato starch.

4. The adhesive of claim l wherein said solid siliceous material is akaolinitic clay.

5. The adhesive of claim 1 wherein the composition is free from saidfinely-divided solid siliceous material and has a filter test notsubstantially exceeding 30 cc. and a Viscograph curve whose knee lies ata viscosity of from about 0.2 to 3 poises and at a temperature of fromabout 60 to 75 C.

6. The adhesive of claim 1 wherein the composition contains from l to 25percent of clay as a siliceous material and which has a filter testwithin the range of from about 2 to 20 cc. and a Viscograph curve whoseknee lies at a viscosity of from about 0.2 to 3 poises and at atemperature of from about 70 to 85 C.

7. An adhesive particularly adapted for use in the high-speedmanufacture of combined ber board, which comprises from about 2 to 5percent by weight of starch, from about 4 to 10 percent by weight ofclay, from about 20 to 100% by weight of an alkali metal borate based onthe weight of the starch, all dispersed in an aqueous solution of sodiumsilicate constituting from about 75 to 90 percent of the adhesive as awhole; said sodium silicate having a percent ratio of Naz to SiOz withinthe range of from about 1:2.5 to 1:4 and said solution having aviscosity within the range of from about 0.25 to l5 poises and a gravityof from about 30 to 50 B. at 20 C.; the adhesive having an over-allviscosity at operating temperatures of from about 0.5 to 15 poises and afilter test at operating temperatures of from about 3 to 15 cc.

8. In the manufacture of laminated paper board on high-Speed laminatingmachines wherein at least two plies are combined with an adhesivecontaining a sodium slicate solution as its aqueous phase having aviscosity within the range of from about 0.25 to 15 poises and a gravityof from about 30 to 50 B. at 20 C. with a percent ratio of NaOz to SiOzwithin the range of from about 1:2 to 1:4.2 and containing substantiallyuniformly dispersed therein from about 1.5 to 10 percent by weight of araw unswelled starch-like material which has the property of swelling byhydration before going into solution when heated in water totemperatures within the range of from about 55 to 80 C., from about 15to 150 percent by weight of an alkali metal borate based on thestarch-like material in the adhesive, and usually from about 1 to 25percent by weight of a timely-divided solid siliceous material having anaverage particle size not substantially exceeding 2 microns; the saidsilicate solution constituting at least about 50 percent of the adhesiveas a whole; the said adhesive having an over-all viscosity at operatingtemperatures of from about 0.2 to 15 poises, a filter test at operatingtemperatures of from about 2 to 20 cc. and, in the case of compositionsfree from clay, up to about 30 cc., and having a Viscograph curve with aknee at a viscosity of from about 0.2 to 3 poises which lies betweenabout 70 and 85 and, in the case of compositions free from clay, betweenabout 60 and 75 C. and having the characteristic property of increasingin viscosity at a rate substantially higher than that of a similaradhesive free from said alkali metal borate when heated to ternperatureswithin the range of from about 55 to 90 C.; the process which comprisesapplying to the face of a ply to be laminated the adhesive definedabove, immediately combining the adhesive-coated face with another plyunder pressure and heating the adhesive substantially simultaneouslywith its application to temperatures within the range of from about 55to 90 C., whereby u ash bond is produced capable of withstandingcutting, scoring and other mechanical operations and stronger than thatproduced by a similar adhesive free from said borate.

9. The process of claim 8 wherein the adhesive used contains akaolinitic clay as the finely-divided solid siliceous maten'al.

10. The process of claim 8 wherein the adhesive is heated just prior toits application to temperatures within the range of from about 40 to 80C.

11. The process of claim 8 wherein at least one of the plies to becombined is preheated to temperatures within the range of from about 80to 105 C.

12. The process of claim 8 wherein the adhesive is preheated totemperatures within the range of from about 40 to 80 C. and at least oneof the plies is preheated to temperatures within the range of from about80 to 105 C.

13. The process of claim 8 wherein the adhesive is preheated totemperatures within the range of from about 40 to 80 C. and the aqueousphase of said adhesive has a viscosity of from about l to 8 poises and agravity of from about 32 to 50 B. at 20 C.

14. The process of claim 8 wherein the adhesive is applied atsubstantially room temperatures and the aqueous phase of said adhesivehas a viscosity of from about 14 0.25 to 1.5 poises and a gravity withinthe range of from about 30 to 48 B. at 20 C.

l5. The process of claim 8 wherein the laminated product is a solidfiber board and the over-all viscosity of the adhesive at operatingtemperatures is within the range of from -about 5 to 15 poises.

16. The process of claim 8 wherein one of the plies is corrugated andthe adhesive used has an over-al1 viscosity within the range of fromabout 0.5 to 5 poises at operating temperatures.

17. In the manufacture of laminated paper board on high-speed laminatingmachines, the process which comprises applying to the face of a ply tobe laminated the adhesive dened in claim 7, immediately combining theadhesive-coated face with another ply under pressure and heating theadhesive substantially simultaneously with its application totemperatures within the range of from about 55 to 90 C., whereby a ashbond is produced capable of withstanding cutting, scoring and othermechanical operations and stronger than that produced by a similaradhesive free from alkali metal borate.

References Cited in the lle of this patent UNITED STATES PATENTS1,147,996 Wrede July 27, 1915 2,239,478 Amberson Apr. 22, 1941 2,529,851Scrutcheld Nov. 14, 1950 2,610,136 Casey et al. Sept. 9, 1952 2,669,282Kreyling Feb. 16, 1954

8. IN THE MANUFACTURE OF LAMINATED PAPER BOARD ON HIGH-SPACED LAMINATINGMACHINES WHEREIN AT LEAST TWO PILES ARE COMBINED WITH AN ADHESIVECONTAINING A SODIUM SILICATE SOLUTION AS ITS AQUEOUS PHASE HAVING AVISCOSITY WITHIN THE RANGE OF FROM ABOUT 0.25 TO 15 POISES AND A GRAVITYOF FROM ABOUT 30 TO 50* BE. AT 20* C. WITH A PERCENT RATIO OF NAO2 TOSIO2 WITHIN THE RANGE OF FROM ABOUT 1:2 TO 1:4.2 AND CONTAININGSUBSTANTIALLY UNIFORMLY DISPERSED THEREIN FROM ABOUT 1.5 TO 10 PERCENTBY WEIGHT OF A RAW UNSWELLED STARCH-LIKE MATERIAL WHICH HAS THE PROPERTYOF SWELLING BY HYDRATION BEFORE GOING INTO SOLUTION WHEN HEATED IN WATERTO TEMPERATURES WITHIN THE RANGE OF FROM ABOUT 55* TO 80* C., FROM ABOUT15 TO 150 PERCENT BY WEIGHT OF AN ALKALI METAL BORATE BASED ON THESTARCH-LIKE MATERIAL IN THE ADHESIVE, AND USUALLY FROM ABOUT 1 TO 25PERCENT BY WEIGHT OF A FINELY-DIVIDED SOLID SILICEOUS MATERIAL HAVING ANAVERAGE PARTICLE SIZE NOT SUBSTANTIALLY EXCEEDING 2 MICRONS: THE SAIDSILICATE SOLUTION CONSTITUTING AT LEAST ABOUT 50 PERCENT OF THE ADHESIVEAS A WHOLE; THE SAID ADHESIVE HAVING AN OVER-ALL VISCOSITY AT OPERATINGTEMPERATURES OF FROM ABOUT 0.2 TO 15 POISES, A FILTER TEST AT OPERATINGTEMPERATURES OF FROM ABOUT 2 TO 20 CC. AND, IN THE CASE OF COMPOSITIONSFREE FROM CLAY, UP TO ABOUT 30 CC., AND HAVING A VISCOGRAPH CURVE WITH AKNEE AT A VISCOSITY OF FROM ABOUT 0.2 TO 3 POISES WHICH LIES BETWEENABOUT 70* AND 85* AND, IN THE CASE OF COMPOSITIONS FREE FROM CLAYBETWEEN ABOUT 60* AND 75* C. AND HAVING THE CHARACTERISTIC PROPERTY OFINCREASING IN VISCOSITY AT A RATE SUBSTANTIALLY HIGHER THAN THAT OF ASIMILAR ADHESIVE FREE FROM SAID ALKALI METAL BORATE WHEN HEATED TOTEMPERATURES WITHIN THE RANGE OF FROM ABOUT 55* TO 90* C.; THE PROCESSWHICH COMPRISES APPLYING TO THE FACE OF A PLY TO BE LAMINATED THEADHESIVE DEFINED ABOVE, IMMEDIATELY COMBINING THE ADHESIVE-COATED FACEWITH ANOTHER PLY UNDER PRESSURE AND HEATING THE ADHESIVE SUBSTANTIALLYSIMULTANEOUSLY WITH ITS APPLICATION TO TEMPERTURES WITHIN THE RANGE OFFROM ABOUT 55* TO 90* C., WHEREBY A FLASH BOND IS PRODUCED CAPABLE OFWITHSTANDING CUTTING, SCORING AND OTHER MECHANICAL OPERATIONS ANDSTRONGER THAN THAT PRODUCED BY A SIMILAR ADHESIVE FREE FROM SAID BORATE.